1. Technical Field
The disclosure relates in generally related to a semiconductor device and the method for fabricating the same, and more particularly to a split gate non-volatile memory (NVM) device and the method for fabricating the same.
2. Description of the Related Art
An non-volatile memory (NVM) device which is able to continually store information even when the supply of electricity is removed from the device containing the NVM cell has been widespreadly adopted by bulk solid state memory applications in the art.
Split gate memories are a type of non-volatile memory (NVM) that have a control gate and a select gate disposed between two doped regions that are for use as the source and the drain. Typically, the control gate of a split gate NVM cell is disposed over a storage medium that may be a floating gate or a thin film storage layer of nitride. Currently, in order to scale down the split gate structure of the split gate NVM cell and to solve the problems associated with misalignment of the gates and the respective drain and source regions, an oxide-nitride-oxide (ONO) layer is used for serving as the storage medium and the select gate is fabricated by using self-alignment techniques.
However, the self-aligned select gate has ununiformed thickness due to bad etch uniformity control, and the implant ions (such as the implant ions of the light-doped-drain (LDD) implantation) penetrating into the thinner portions of the self-aligned select gate to cause the threshold voltage (Vt) of the self-aligned select gate shift. Such that, hard error of memory cells may be induced by the Vt shift.
Furthermore, as is typical of a NVM cell in general, endurance and data retention are important issues. However, the endurance and data retention of the split gate NVM cell may be deteriorated due to the accumulation of hot holes trapped after several program/erase operations are performed at the point where the ONO layer is discharged through band-to-band hot hole tunneling (BTBHH) near the drain side of the split gate NVM cell mismatching with the point of electrons injection through Fowler-Nordheim tunneling occurring near the source side of the split gate NVM cell.
Therefore, there is a need of providing an improved split gate NVM device and the method for fabricating the same to obviate the drawbacks encountered from the prior art.